As the thermometer reached toward 90 degrees the other day for the first time this year, thoughts turned to springtime – new flowers blooming, the smell of citrus and jasmine and the lovely allergies they bring – and of course, spring vaccinations for our horses. OK, so the latter probably did not pop into your head, but it should, especially in the desert and in Florida. I was a bit shocked the other evening when I was at a local ranch treating a horse only to see a little mosquito land on my arm – after only a couple days of 80 degree weather. It has been pretty cold this winter, but how quickly the little pests show up.
While guidelines for vaccinations in the horse vary from time to time and place to place, I’ll try and present a basic protocol that is useful just about anywhere in the US and Canada. In general, a 2-dose series 4-6 weeks apart is usually required for first-time vaccinations. Pregnant mares should receive their vaccinations 4-6 weeks before their foaling date in an effort to concentrate antibodies in the colostrum so that adequate transfer can take place to the foal.
Tetanus – this infection is caused by a Clostridium bacteria that is present in the intestinal tracts of most animals and humans and is pretty prevalent in the soil. Deep puncture wounds to the feet and muscles are usually the most risky to the horse. Umbilical cords of foals are also a source of infection and this has probably led to the practice of “dipping the navel” in an antiseptic solution after birth. Vaccination in adult horses is done annually, usually in the spring. The horse receives good immunity and may very well last longer than a year. Foals should not be vaccinated until they are 4-6 months old.
Encephalomyelitis (“Sleeping sickness”) – The main diseases here are Eastern and Western Equine Encephalomyelitis (EEE and WEE) and for the most part they occur in the respective part of the United States. Venezuelan Equine Encephalomyelitis (VEE) is fairly well restricted to South and Central America – it has not been diagnosed in the US for over 20 years. These diseases are transmitted by mosquitoes so it is very important to vaccinate ahead of the mosquito season. Obviously that differs throughout the country, as there are not too many of the little buggers in Chicago right now where I grew up. Give them a few months though and they will become the state bird. But as stated earlier, they are already showing up in the desert southwest and probably in Florida also. This is a deadly disease when it occurs. WEE has about a 50% mortality rate, while EEE can reach close to 90% mortality. This is an annual vaccine and should be given in the spring, probably no later than April. Foals should be vaccinated around 4-6 months of age.
West Nile Virus – While we are on the subject of mosquito bashing, do not think West Nile virus has gone away. Since 1999, over 24,000 cases of this disease have been reported in US horses alone. The good news is that the numbers are dropping dramatically – a little more than a 1000 cases in 2006 and down to 250 cases by October 2007. This is a direct result of vaccination and acquired immunity in the horse population. Even so, horses represent 97% of all non-human mammalian cases of West Nile virus. Just like EEE and WEE, vaccinate in the spring ahead of the mosquito season. It is very important to make sure any unvaccinated horse receives a 2-dose series initially. Even though immunity is supposed to last a year or more, semiannual boosters are usually given. Most vaccines do not come with recommendations for pregnant mares, but most veterinarians feel the risks of infection far outweigh the risk of vaccination. Foals should be vaccinated at 4-6 months.
Equine Herpesvirus (Rhinopneumonitis) – Without getting too in depth, herpes virus can manifest itself in the horse as a respiratory form, a neurological form or as abortion in pregnant mares. There are 2 basic types found – EHV-1 and EHV-4. Both can cause respiratory infections, while EHV-1 has more often been associated with abortion and neurological disease. This may be an oversimplification, but you get the picture. To make matters even more confusing, there are various types of vaccines available – inactivated and modified–live. And of the inactivated type, one seems to have been produced specifically for pregnant mares. Anyway, pregnant mares are vaccinated at 5, 7 and 9 months of pregnancy with the inactivated vaccine. The frequency of vaccination of other horses varies depending on the area and use of the horse. It is common place for racing, show and polo horses to receive this vaccine every 2-3 months. The back yard trail horse that does have much exposure to other horses is probably fine with getting vaccinated 2 times a year. As we have seen in the past year, even well vaccinated horses are susceptible to this disease on rare occasions.
Influenza – I am sure those of you that got a flu shot this year and came down with the “Indio crud” anyway really do not want to hear about the benefits of vaccinating your horse for the flu. Well, it is the same thing for equines – lots of different strains of flu and you just hope the ones you vaccinated for are the only ones around. There are 2 things we know – horses under 5 years of age and those that come into contact with large numbers of other horses are more susceptible to influenza infections. Common sense says to vaccinate and hope for the best. Again there is some variety in the type of vaccines available, not only inactivated intramuscular types but a modified live intranasal vaccine. Again the frequency can be similar to the herpesvirus vaccination – more often for show, polo and race horses that are in contact with large numbers of horses and less often for the more isolated horses. One difference is that foals are not recommended for their first vaccination until 6 months of age.
Strep. equi (Strangles) – the dreaded infection!! Sorry, but it is here in the desert and it is here to stay. This is not a viral but a bacterial infection (Strep. throat for horses) and thus it is a little harder to get protection against. If your horse has ever come down with it, you know it is messy, it is ugly and it can be downright disgusting. It can also be very contagious. So if you do have a horse come down with this infection, please do us all a favor and get it as far away from other horses as possible and as isolated as you can. There are really on 2 bacterins for this disease – an intramuscular and an intranasal form. Personally, I prefer the intranasal form but I am sure there are other veterinarians that do not. In any case, the immunity is short-lived and it should be given at least 2 times a year.
While there are other diseases to vaccinate for – rabies, Potomac Horse Fever and on and on, I feel the ones mentioned above are sufficient in most cases. Certain regions may warrant a different protocol.
So in a nut shell, what is a good basic vaccination program?
Spring time vaccinations:
5-way (EEE, WEE, Tetanus, Influenza and Rhinopneumonitis)
West Nile Virus
Strangles
Summer
West Nile booster
Fall
Strangles
Flu/Rhino booster (intranasal flu and modified live rhino)
Keep yourself safe and your horses healthy. Until next time….